As a method of printing on a to-be-printed member, an inkjet scheme is available which prints by discharging liquid droplets from a nozzle formed in a head. Among those that employ this scheme, a printer that prints a color image on paper is best known. The inkjet print scheme is applied not only to a printer but also to manufacturing apparatuses such as a color filter manufacturing apparatus, a DNA chip manufacturing apparatus, and the like because it enables a small liquid droplet to land at a predetermined position.
A conventional printer employing the inkjet scheme will be described with reference to FIGS. 24, 25, 26, 27, 28, and 29.
First, the appearance of the conventional inkjet printer will be described with reference to FIGS. 24, 25, and 26.
FIG. 24 is a front view of the conventional inkjet printer, FIG. 25 is a plan view of the same, and FIG. 26 is a side view of the same. Referring to FIG. 24, the outer appearance of a main body 25 is formed of a case 24 and cover 23. The case 24 has a paper feed port 27. As shown in FIG. 25 which is a plan view of the inkjet printer, the cover 23 is connected to the case 24 through hinges 26. As shown in FIG. 26 which is a side view of the inkjet printer, the cover 23 pivots in directions A, as it is connected to the case 24 through the hinges 26.
FIG. 27 is a sectional view taken along the line B-B of FIG. 24, and FIG. 28 is a sectional view taken along the line C-C of FIG. 26. As shown in FIG. 27, a carriage 1 is attached, through a belt fixing portion 5, to a belt 4 attached to a pulley 3 to which the driving force from a main scanning motor 2 is transmitted. When the main scanning motor 2 is driven, the carriage 1 moves in directions D. At this time, the carriage 1 moves as it is supported by a main rail 28 and subrail 29. Ink cartridges for storing ink are mounted on the carriage 1. The number of ink colors is four, i.e., Y (yellow), M (magenta), C (cyan), and BK (black), and the number of ink cartridges, although not shown, is also four.
As shown in FIG. 28, a head 6 attached to the carriage 1 is capped with a cap 7 when it does not print. The head 6 has 256 nozzles for each color, so that it can discharge inks of four different colors. A wiper 8 which cleans the head 6 after printing is attached in a wiper case 9, and the wiper case 9 is supported by a support plate 10. The support plate 10 is attached to a side plate (R) 11. A spare discharge box 12 is arranged next to the wiper case 9. The spare discharge box 12 receives the ink which is discharged from the head 6 before printing to hold the meniscus of the nozzles of the head 6 at a constant level. The spare discharge box 12 is attached to the support plate 10, and the support plate 10 is attached to the side plate (R) 11.
A waste liquid tube 14 is attached to the spare discharge box 12, and is connected to a waste liquid absorber 13. Thus, the ink discharged from the head 6 into the spare discharge box 12 flows through the waste liquid tube 14 and is absorbed by the waste liquid absorber 13. The cap 7 is connected to a suction pump (not shown) through a suction tube 21. After the cap 7 is brought into tight contact with the head 6, the suction pump is actuated, so that small dust, bubbles, and inks with high viscosities are drawn by suction from all the nozzles (256 nozzles for each color) formed in the head 6 (One function of the discharge apparatus for removing a medium such as small dust in a nozzle is generally called a recovery unit portion hereinafter).
FIG. 29 is a sectional view, taken along the line E-E of FIG. 28, and shows a case wherein the carriage 1 has moved to the left from the sectional line E-E in FIG. 28 and a printing sheet 15 is inserted. The printing sheet 15 is inserted in a direction F and is delivered in a direction G. When the printing sheet 15 is inserted in the direction F, it is clamped between a manual feed roller 17 and driven roller 16, and is fed in a direction H by them. After that, the printing sheet 15 passes on a platen 20, is clamped between a feed roller 19 and driven feed roller 18, is fed in the direction H, and is delivered through a delivery port 22. When the printing sheet 15 is present on the platen 20, the head 6 attached to the carriage 1 discharges ink onto the printing sheet 15, thus forming an image on the printing sheet 15.
As described above, in the discharging apparatus such as the conventional inkjet printer, inks of different colors from the nozzles are drawn by suction with one cap 7.
Hence, in supplying different inks to the plurality of nozzles, when some nozzle is left without being injected with any ink, if suction is performed from all the nozzles simultaneously by using one cap that covers the plurality of nozzles entirely, as in the prior art described above, a problem arises in that air is undesirably drawn by suction from the nozzle in which no ink has been injected, and the ink cannot be drawn by suction from the nozzle injected with the ink.
After suction, since all the liquids are mixed in one tank, the collected liquid mixture forms a waste liquid, and cannot be used again in any other way. In other words, suction which is performed to improve the quality of printing leads to a mass disposal of valuable liquids. As a result, the cost necessary for using the discharging apparatus increases.